sohail@terak.UUCP (Sohail M. Hussain) (12/13/84)
As the title suggest, I am wondering if there is a standard for 3 1/2 inch floppy formats. I am about to start using a 3 1/2 floppy on our new machines, and I get to decide what format we will use. Since we have never had 3 1/2 inch drives before, I have no constraints to be compatible with any of Terak's past products. I am interested in being compatible with some standard that exists or is emerging. The drives we are using are TEAC 35F, which are double sided double density, 80 cylinders. The format I was planing on using, and of course I would change if some one has a better idea, is based on IBM 3740, and is as follows: Side 0, Cylinder 0 would be FM. Sector 7 of this track would be used for identifying the media characteristics. The rest of the track would be availible for use. This track would not be visible to the OS, (in our case UNIX) through the normal read/write command, but would be accessed through ioctl calls. Density | Recording | Bytes/ | Sectors/ | capacity | mode | sector | Track | in Kbytes --------+-----------+--------+----------+---------- SSSD | FM | 128 | 16 | 158 --------+-----------+--------+----------+---------- SSDD | FM (trk 0)| 128 | 16 | | MFM (rest)| 256 | 16 | 316 --------+-----------+--------+----------+---------- DSDD | FM (trk 0 | 128 | 16 | | side 0)| | | | MFM (rest)| 256 | 16 | 636 --------+-----------+--------+----------+---------- SSSD=Single Sided Single Density SSDD=Single Sided Double Density DSDD=Double Sided Double Density An alternative scheme that I am considering is as follows: Density | Recording | Bytes/ | Sectors/ | capacity | mode | sector | Track | in Kbytes --------+-----------+--------+----------+---------- SSSD | FM | 128 | 16 | 160 --------+-----------+--------+----------+---------- SSDD | MFM | 512 | 8 | 320 --------+-----------+--------+----------+---------- DSDD | MFM | 512 | 8 | 640 --------+-----------+--------+----------+---------- As to the interleave factor, I am still playing with that to try and determine a good value for it. The two candidates that I have in mind are 1. no interleave, for simplicity. 2. same as DEC RX01 Ofcourse one can not talk about 3 1/2 floppies with out thinking of the MAC. I have been told that they are single sided only and they rotate at a different speed (compared to the TEAC drives) To conclude, I would be interested in hearing from people on the subject of 3 1/2 floppy format being used today, as well as comments on the two formats listed above. I will ofcourse post a summary if there is much interest sohail -- Sohail Hussain uucp: ...{decvax,hao,ihnp4,seismo}!noao!terak!sohail phone: 602 998 4800 us mail: Terak Corporation, 14151 N 76th street, Scottsdale, AZ 85260